This invention relates to apparatus for monitoring a.c. electric quantities, such as electric currents, voltages, and charges. Apparatus according to this invention is particularly useful in supervisory control of an electric power system.
In a control system for an electric power system, high-speed operation is more and more important as the power system becomes greater in scale and intricate in construction and as the voltage on the transmission line is rendered higher. On the other hand, it is already known that application of digital techniques to supervision of a.c. electric quantities is preferable in such a supervisory control system. The reasons are described in U.S. Pat. application Ser. No. 386,382 filed Aug. 7, 1973, by Toshio Takagi, assignor to Tokyo Denryoku Kabushiki Kaisha, one of the instant assignees. For high-speed operation, it is desirable to derive a control signal of a monitoring or supervisory control system from a small number of analog or digital samples of the electric quantities being monitored. In addition, it has been heretofore necessary to synchronize sampling pulses used at different points of a supervisory control system even where unnecessary according to the present invention.